Philologists may be interested enough to find out when this word ‘ecology’ became part of the language. Its frequent use in scientific writing today is a portent. The sister-word ‘economy’ has reflected the history of much of our modern thinking about man and mankind in the emphasis laid, not on ‘goods’ themselves as such, but on commerce in and distribution of such goods. Just as, from Devas onwards, there is a growing tendency among economists to consider human, as well as material, factors in the definition of such ideas as prosperity, so a new branch of science has found it increasingly necessary to study in detail what one may call the raw materials of prosperity.

Materially speaking, there are two main aspects of the environment of homo sapiens that repay modern study. One may be summed up under the term exterior influences—climate, housing, clothing, and the like. The others, subject of this short essay, are internal: in a word, man’s diet.

Time was when science seemed to have summed up the whole matter of the human body and how it is nourished, in the three magic words: proteins, fats, and carbohydrates. But already the biochemists were beginning to analyse the individual components of each of these, and the necessity for certain minerals—at first the list was limited to iron and calcium—was emphasised, together with observations of their deficiency in the diet of civilised man. A little later, first Lunin and then Hopkins proved that there was a missing factor which the latter called ‘accessory food substances’ and to which Funk gave the name vitamines.